The present invention relates to electromagnetic fuel injection valves for use in internal combustion engines.
In conventional internal combustion engines for automobile use, an electromagnetic fuel injection valve driven by the electrical signals sent from the engine control unit is commonly used.
This type of fuel Injection valve is constructed so that: an electromagnetic coil and a yoke are arranged around a hollow tubular type of fixed core (center core); a nozzle body containing a needle equipped with a valve body is installed at the bottom of the yoke which accommodates the electromagnetic coil, and; the needle is energized towards the valve seat by the action of the return spring.
Proposed an example of such a conventional electromagnetic fuel injection valve is, as disclosed in, for example, Japanese application patent laid-open publication No. Hei-10-339240 or Hei-11-132127, a single one into which a magnetic fuel connector portion, a non-magnetic intermediate pipe portion, and a magnetic valve body portion were molded by magnetizing one pipe formed of a composite magnetic material and then non-magnetizing only the intermediate portion of this pipe by use of, for example, induction heating, in order to reduce the number of parts and facilitate the assembly of the parts.
For this type, a cylindrical fixed core is press-fit in a fuel connector portion and a movable core with a valve body is mounted in the valve body portion. Also, an electromagnetic coil is provided on the intermediate periphery of the pipe and a yoke is provided outside the electromagnetic coil. When power is supplied to the electromagnetic coil, a magnetic circuit is formed over the area from the yoke to the fuel connector portion, the fixed core, the movable core, the valve body portion, and the yoke, and the movable core is magnetically attracted towards the fixed core. The non-magnetic portion functions as a magnetic flux short-circuiting suppressor between the fuel connector portion and the valve body portion.
In recent years, even in a gasoline engine, a fuel injection valve that directly injects a fuel into the cylinders of the internal combustion engine is placed in practical use.
A so-called xe2x80x9clong nozzle type of injectorxe2x80x9d having a thin and long nozzle body at the bottom of its yoke is also proposed for the direct injection type of fuel injection valve mentioned above. When this long nozzle injector is installed on the cylinder head of an engine, if the periphery of the cylinder head is crowded with parts such as an air intake valve and an air intake pipe, only the slender nozzle body which does not take too large a space can be positioned on the cylinder head and the yoke, the connector mold, and other large-diameter valve portions can be spaced from other parts and the cylinder head to avoid interference. Therefore, this type of injector has the advantage that the flexibility of its installation is very high.
An object of the present invention is to supply a compact, electromagnetic fuel injection valve reduced in dimensions, especially in diameter, provided with an inexpensive and sufficient magnetic circuit, and excellent in performance, so as to make the main unit of the fuel injection valve suitable for injection schemes such as the direct intra-tubular injection scheme set forth above.
Another object of the present invention is to supply an electromagnetic fuel injection valve capable of suppressing the restitution of a closed valve body and preventing the occurrence of problems such as secondary fuel injection.
In order to accomplish the objects mentioned above, various inventions are proposed herein. The essentials of these inventions are described below.
An electromagnetic fuel injection valve basically having, as the major elements constituting the fuel flow channel in the axial direction of the injection valve body,
a fuel induction pipe,
a hollow tubular type of fixed core equipped with a flange at its top end, and
a nozzle holder that was press-machined into a slender and tubular shape using a pipe and has an orifice plate equipped with a valve seat at the lower end of said nozzle holder,
is characterized in that:
said pipe is connected by welding to the top of the flange of the fixed core mentioned above, the upper inner surface of said nozzle holder and the outer surface of the fixed core are connected by press-fitting and welding, and one fuel flow channel assembly is thus constituted,
said fuel flow channel assembly contains a needle connecting a movable core to the valve body, a return spring for energizing this needle in the direction of said valve seat, and a member for adjusting the spring action of said return spring, and
an electromagnetic coil is provided at a peripheral position on said nozzle holder at which the nozzle holder and the fixed core are press-fit, and outside the electromagnetic coil is positioned a tubular yoke whose upper end is connected by welding to the flange of the fixed core and whose lower end is press-fit on the outer surface of the nozzle holder.
Also, an electromagnetic fuel injection valve having
a needle equipped with a valve body,
a return spring for applying a spring load to the valve seat side of said needle,
an electromagnetic coil, and
a magnetic circuit for magnetically attracting said needle in the opening direction of the valve by the excitation of said electromagnetic coil,
is characterized in that:
said needle has a movable core operating as an element of said magnetic circuit,
said movable core and said valve body are connected via a joint having a spring function,
a plate spring is built into said needle, and
an axially movable mass body is positioned, independently of said needle, between said return spring and said plate spring.